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Single Idea 16521
[filed under theme 9. Objects / F. Identity among Objects / 6. Identity between Objects
]
Full Idea
The famous proof of Barcan Marcus about necessity of identity comes down to simply this: Hesperus is necessarily Hesperus, so if Phosphorus is Hesperus, Phosphorus is necessarily Hesperus.
Gist of Idea
A is necessarily A, so if B is A, then B is also necessarily A
Source
David Wiggins (Sameness and Substance [1980], 4.3)
Book Ref
Wiggins,David: 'Sameness and Substance' [Blackwell 1980], p.110
A Reaction
Since the identity of Hesperus and Phosphorus was an a posteriori discovery, this was taken to be the inception of the idea that there are a posteriori necessities. The conclusion seems obvious. One thing is necessarily one thing.
The
21 ideas
with the same theme
[two objects turning out to be one object]:
15847
|
Two things relate either as same or different, or part of a whole, or the whole of the part
[Plato]
|
24254
|
Two existing entities can never strictly coincide
[Plato]
|
15825
|
Carneades denied the transitivity of identity
[Carneades, by Chisholm]
|
9853
|
Identity between objects is not a consequence of identity, but part of what 'identity' means
[Frege, by Dummett]
|
18440
|
Identity of physical objects is just being coextensive
[Quine]
|
17036
|
Identity statements can be contingent if they rely on descriptions
[Kripke]
|
17038
|
If Hesperus and Phosophorus are the same, they can't possibly be different
[Kripke]
|
9905
|
Identity statements make sense only if there are possible individuating conditions
[Benacerraf]
|
16224
|
There can't be vague identity; a and b must differ, since a, unlike b, is only vaguely the same as b
[Evans, by PG]
|
16521
|
A is necessarily A, so if B is A, then B is also necessarily A
[Wiggins]
|
14073
|
Claims on contingent identity seem to violate Leibniz's Law
[Gibbard]
|
15969
|
Two things can never be identical, so there is no problem
[Lewis]
|
6047
|
All identity is necessary, though identity statements can be contingently true
[McGinn]
|
5494
|
'Lightning is electric discharge' and 'Phosphorus is Venus' are synthetic a posteriori identities
[Lycan]
|
15074
|
We would understand identity between objects, even if their existence was impossible
[Fine,K]
|
16027
|
If two things are equal, each side involves a necessity, so the equality is necessary
[Gallois]
|
16231
|
Occasional Identity: two objects can be identical at one time, and different at others
[Gallois, by Hawley]
|
14081
|
Identities can be true despite indeterminate reference, if true under all interpretations
[Schaffer,J]
|
16360
|
Identity statements are informative if they link separate mental files
[Recanati]
|
14477
|
Identical entities must be of the same category, and meet the criteria for the category
[Thomasson]
|
14476
|
Identity claims between objects are only well-formed if the categories are specified
[Thomasson]
|